Selective call receivers, including pagers, are widely used to disseminate business and other information. Alphanumeric, voice or tone-only messages can be delivered by radio transmission from a network system. Some network systems have a localized coverage area, some even solely within one building such as a hospital. These network systems are called on-site paging network systems. Other network systems, called wide area network systems, allow for transmission of messages over a large area. In this manner, a selective call receiver can receive messages anywhere within an urban area, or even statewide. Nationwide and international paging schemes are being developed to allow for messages to be forwarded from an originating network system to a network system wherein the transmission can be received by the pager wearer.
In on-site paging systems such as those used in hospitals, it is necessary for the pager wearer to manually inform the network system when he is no longer within the coverage area. Once informed, the system can route incoming pages to the surrounding wide area system, or to whatever alternate system is designated. If the pager wearer is a doctor and receives an emergency call to proceed to a location outside the hospital within the coverage area of the wide area system, he must take the time to call up the paging network system and advise it of his departure from the coverage area. The system would then route his pages to the wide area network system for transmission. If the doctor is detained within the hospital after the network system begins transmitting his pages on the wide area system, he may not receive those pages. Also, if the doctor is in such a hurry as to forget or not be able to take the time to call the on-site network system, the doctor will not receive any of his pages during his time outside the on-site system's coverage area.
Nationwide paging schemes, such as that discussed in U.S. Pat. No. 4,178,476, allow for a message to be passed from one network system to another after the pager wearer has informed the network system of his intent to depart the coverage area and, upon his arrival at his destination, after the pager wearer has again called the network system to inform it of his arrival at his destination. The drawback of this scheme is that it requires two actions on the part of the pager wearer to avoid lost messages.
Thus, what is needed is a scheme for automatically transferring transmission from one paging network system to another upon the first network system determining that the pager wearer is no longer within its coverage area.